Effect of different direct drilling and conventional sowing techniques on soil strength, root growth and grain yield of wheat on sandplain soils in Western Australia

Abstract

Experiments were conducted to compare different direct drilling and conventional sowing techniques, and describe the effects of these techniques on soil strength, root growth and grain yield of wheat on sandplain soils in the northern wheat-belt of Western Australia. Soil strength was identified as a critical factor affecting root growth; increasing the depth of soil loosening beneath seeding depth with a modified direct drill reduced soil strength relative to that found in the traditional direct drill treatments, and increased rooting density beyond the 10 cm soil depth. As loosening depth increased, there were increases in both shoot growth and grain yields, and water use efficiency also improved. Maximizing the depth of soil disturbance by deep ripping after sowing resulted in the highest grain yields, but the time and cost penalties associated with this tillage operation are substantial and likely to deter its routine use. Modifying a direct drill to loosen soil beneath sowing depth therefore combined the advantages of conventional direct drilling (timeliness, moisture conservation and lower risk of erosion), with those obtained by sowing after cultivation (improved root growth and yield) without the yield penalties associated either with direct drilling or delayed sowing on these soils.